06 - CROSS BREEDING…

Ask most motorsport fans about the most incredible race series ever, and you'll get some predictable answers. Formula One of course, especially in the 1,500bhp turbocharged era of heroes. Endurance racing Gulf Porsche 917s from the 1970s perhaps. And the glory days of 600bhp+ Group B rally racing cars. Of course, that sort of thing's all gone now. Isn't it? Well, no actually. There's an auto sport where the cars are still largely unrestricted, with 600bhp turbo engines, four wheel drive, and crazy speeds. Crazy like 0-60mph in 2.0 seconds – on gravel...

It’s called Rallycross, and as the name suggests, it's a little bit like rallying, a little bit like motocross, but in reality, it's completely different. The basics are simple: a mixed on/offroad course, on a short-circuit racetrack. The top-level Supercars are, essentially, full-bore versions of the compact rally cars you might see in WRC, but with fewer restrictions on power output. A genuine 600bhp, from fire-breathing turbocharged 2-litre engines, in heavily-modified, lightweight, hot-hatch chassis.

As you'd imagine, keeping these beasts in check round a tight, twisty tarmac and dirt circuit takes some doing. Much of the job falls to the driver of course – and Rallycross pilots are acknowledged as some of the most talented racers around.

But the suspension plays a vital part too. And for Öhlins, this is one of the most challenging tasks to deal with. Unlike in any other discipline, you need to combine performance on smooth asphalt and loose dirt, as well as handling massive jumps. All the while, dealing with the stresses of hard braking, tight cornering, and 600bhp driving through all four wheels. Phew!

It's a really tough job, with enormous demands made on the suspension.

We spoke to Kenneth Hansen, 14-time European Rallycross champion, and owner of the Hansen Motorsport Peugeot Rallycross team, about the special requirements of the sport.

What are the most important aspects of suspension performance in Rallycross?

"We need some long wheel travel depending on the circuit, if it's wet or dry and how much gravel there is. But it can be like a tarmac race car also, with long wheel travel, much longer than a race car. Because we have dips and holes in the gravel sections, we need to adapt to that. The goal is to always have four wheels on the ground."

This tough job falls to Öhlins' ALR TPX and TTX shocks. These suspension units use Öhlins' tried and tested technology, with twin tube dampers in the TTX units. They're specially developed to give the long suspension travel needed for high-speed jumps, yet provide the precise wheel control needed for optimum grip on tarmac and dirt. They have the massive range of adjustment needed for setup on different courses, combined with extremely fine gradations of damping adjustment, for the perfect setting.

The Hansen Motorsport Team uses custom-made Macpherson-strut type shocks. Kenneth told us how the team puts a lot of work into their setup for each track.

"During the season we try different evolutions and different settings. In a season like this has been, we always are progressing, and hopefully trying new dampers and new things.

"On some tracks without jumps where the surface is quite flat, you can go much more like a racing car. But if you have jumps and holes and kerbs (which the drivers want to cut quite heavily!) then you need to adapt the suspension, so the car can handle this."

Like all race teams, knowledge and experience is vital for Hansen. "We know in advance approximately which level we need to start with at each circuit and then we make adjustments from there. So it can be quite different between say the circuit with the most gravelly sections, to the circuit with the most tarmac. Depending also how the gravel sections are, there's quite a big difference between those."

Does the team experiment a lot with spring rates and wheel travel?

"Yes! We also work a lot with the springs and roll bars, and also ride height changes. The amount of wheel travel we run is confidential, but most of the cars are using up to perhaps 250mm. You can see in the race different wheel travel with different car setups. It's quite similar to a rally car setup."

And you only need to watch one Rallycross race to see what a pounding the dampers take. The enormous wheel travel needed to cope with the jumps gives the suspension a real headache when the cars head into a corner. As the huge brakes slam the cars onto their nose, and the 600bhp engines slingshot them round the bend, the suspension units put in a heroic performance, trying to keep the tyres on the deck, to transmit all that power into the ground.

Normal suspension units would quickly overheat and fade, giving the performance of underdamped pogo sticks on each corner of the car. But Öhlins' advanced technologies keep working, holding the damping oil temperature down, self-adjusting the oil flow to balance the changes in viscosity, and preventing cavitation in the oil chambers.

Extreme stuff. And it's the ability to cope with the two extremes of setup – rally and road - which makes Öhlins suspension the perfect choice. As Kenneth Hansen says, "Our suspension setup is difficult because we work between two extremes – the total offroad rally setup, and the on-road tarmac setup, so we need to use the one that is giving the best lap time. On some circuits it’s difficult to handle the jumps very well if you want a good time, so then you need to sacrifice something. Since last year we learned to work with that, so we are better this year than last year. So it’s going in the right direction."

The 2015 Rallycross season finished, with an exciting round at the Argentinian track at the Autodromo Rosario. But the 2016 calendar has just been released – so you can plan your visit to this most extreme turbocharged auto sport next season! More info at: www.fiaworldrallycross.com

The Cars

Most small hot-hatch cars make up to 200bhp in road trim. But a typical RX car, like the Team Peugeot-Hansen Peugeot 208 makes more than 600bhp… We asked Kenneth Hansen how they do it.

"With a turbo engine today it’s not so difficult to make a lot of power. We have an air intake restrictor on the car of 45mm, [modern rally cars have a 34mm restrictor, allowing about 300bhp] so 600bhp is the most we can get.

Without the restrictor we could get 1,000bhp, which wouldn't suit so well! The level of engine performance on these cars, on these tracks, with the weight (1,300kg) makes quite a good balance. The car is geared for approximately 210kph, depending on the track, about 130-140mph."

And the performance is incredible – the Hansen Peugeot 208 can hit 60mph in around two seconds, even with a manual six-speed gearshift, and no driver aids! The car is based around a stock Peugeot 208 bodyshell, with a Sadev gearbox, running on special Cooper-Avon WRX tyres.